1. Field of the Invention
The present invention relates generally to subsea well installations, more specifically, to a flowline apparatus for connecting a flowline to a subsea well installation.
2. Background of the Prior Art
Different structures are placed on or buried in the seabed for subsea oil and gas production operations. The structures have mandrels or tubular members to connect to flowlines. Flowlines connect these structures and are typically installed after the structures were placed at the seabed. The lines or piping systems with hubs or connectors at the ends are lowered to the seabed for installation via wire rope guidelines or other running strings such as pipe. The connectors are consequently hard landed on either the subsea mandrel or support structures, and with the aid of remote operated vehicles (ROV) or tools, are locked to subsea flowline mandrels. The mandrels are typically vertical so the flowline connectors lower down on top of them, but the mandrels can be horizontal. If the connector assemblies are landed fast or too hard on the subsea mandrels such that the landing force is not controlled, damage to the hubs and seals can occur.
Flowline connector assemblies are normally run subsea and landed over the subsea flowline mandrels with funnel up, funnel down, or frame and tool assemblies. Here the connector and mandrel are locked and sealed together. Previous assemblies required the ROV to perform numerous operations in order to engage locking members from the remotely run frame to the subsea base structure. Previous assemblies also required the ROV to perform numerous operations to engage locking members on the flowline connector, even after the frame has been secured to the subsea support structure.
In a subsea well installation a subsea flowline with remotely operated connector receptacles is run from a surface vessel on wire rope, or other running strings. In this invention, the flowline and connector are run attached to a frame, which in turn is run on wire rope or pipe. In this case the connector is extended to the upward position relative to the frame, so that when the frame assembly lands and locks to a fixed porch or support plate below the subsea mandrel, the connector will not come in contact with the mandrel, but can be soft landed on the mandrel after the frame assembly is stroked halfway down, locking the frame to the porch or support plate. The fluorine connector receptacle will be positioned above the mandrel where the seal will be installed between the connector and mandrel with the ROV. The connector and frame assembly will then be lowered softly to the mandrel protruding from above the mandrel support porch with an axially stroking mechanism. For replacing the seal, the frame has locking members that allow the frame to be lifted to a partially open position that releases the receptacle mandrel without releasing the frame from the mandrel support. The connection is made by first landing the connector assembly on the mandrel base, then lowering the frame partially to lock the frame to the base, then lowering the frame completely to lock the connector receptacle to the mandrel, making a tight connection without exerting undue forces on the mandrel. The frame can then be raised partially, releasing the connector receptacle from the mandrel while the frame remains locked to the mandrel support, allowing the seal between the receptacle and the mandrel to be replaced without the necessity of re-aligning the connector.
The frame and the receptacle have locking mechanisms that are automatically actuated as the frame is advanced to the mandrel support. The ROV connecting this assembly to the rate mandrel and the mandrel support only needs to operate a lowering device in order to advance the frame to the mandrel support.